Cows and Cows-mkgen share the same format for diagnostic messages so this section will cover both.
Diagnostic messages printed before or after parsing (e.g. an error occurs while trying to open input file) are prefixed by the invocation name for the program:
invocation name: error message
As an example:
$ ./cows dontexist.cws dontexist.html ./cows: unable to get infos about dontexist.cws; No such file or directory
Diagnostic messages printed while parsing are prefixed by file name and line number where reported event occurred:
source-file-name:lineno: message
As an example:
$ cows input.cws output.html input.cws:7: parse error before `else'
If the file containing the error has been included from other files, the whole list is displayed. As an example, if status.cws includes top.cws, which in turn includes table_of_contents.cws you can see something like:
In file included from ./main/infos/status.cws:5,
from ./tools/top.cws:7:
./tools/table_of_contents.cws:15: parse error before `{'
Cows and Cows-mkgen can display four types of diagnostic messages:
Provide user with informations about program's activity. Execution goes on.
$ cows-mkgen cows-mkgen: info: No source file found .. creating empty Makefile
Report an anomaly that may cause trouble. Execution goes on, unless -fatal-warnings (-E) command line option was used.
$ cows input.cws output.html input.cws:4: warning: variable `foo' not defined
Report an anomaly that makes it impossible to get a valuable output. Execution stops, unless -ignore-errors (-i) command line option was used.
$ cows input.cws output.html input.cws:7: parse error before `else'
Same as errors, but execution stops anyway, regardless of -ignore-errors options.
$ cows --ignore-errors input.cws output.html cows: fatal: can't open input file input.cws; Permission denied
You can produce a more verbose diagnostic with the -verbose (-v) option or suppress all messages with the -quiet (-q) or -silent (-s) options.
Also, the -brief (-b) option will produce shorter messages, without changing their amount. Visually impaired users relying on a speech version of shell's output may find this flag useful since large amounts of output can slow down work. If this is your case, also remember that when building your site with Make, you can use make -s instead of make: the former won't print the commands as they are executed reducing the amount of output on your screen.
See Section 6.2 and Section 6.4 for details on command line options for Cows and Cows-mkgen.
This manual can be downloaded from http://www.g-cows.org/.